There are several different differ ent types of lubricants that are typically used in industry, although the basic purpose of the product is the same - to ensure that moving parts operate m ore smoothly and to reduce friction. Using the right lubricant can reduce the need for unscheduled maintenance; help to prolong the life of machine components - and ultimately save money.
Industrial lubricants also vary a great deal in terms of chemical composition - some contain silicon-based fluids, some mineral or petroleum oils, while others may contain natural oils. Some contain high water content and are known as HWCF fluids. Typically, this type of fluid has a high level of heat resistance and also accelerates the cooling process. An example of a solid lubricant that's widely used would be a compound such as hexagonal flake graphite, or boron nitride. Typically, solid lubricants are particularly effective when i t comes to keeping out moisture as well as reducing general wear and tear.
Depending on your needs, you may want to choose a lubricant with a specific feature or characteri stic. Some industrial lubricants are biodegradable, fire resistant or oxidation inhibiting. Many are also odorless and colorless.
Most synthetic fluids offer excellent cooling properties and fire resistance, making them particularly versatile. Synthetic fluids can be used in a diluted form, with concentrations generally ranging from 3% to 10%.
Certain industries need certain lubricants - lubricants used in the food industry are specifically designed to be safe if they come into i nto contact with food. Food processing plants in particular need a lubricant that offers this feature.
An important feature of lubricants is the kinematic viscosity - the tim e that it takes for an amount am ount of fluid to flow through a tube of certain size. Viscosity - or flow - is measured at two differe nt temperatures - 100 degrees F and 210 degrees F.
Some lubricants use additives so that they can withstand a heavy we ight or a rapid movement. So-called extreme pressure (EP) lubricants use chemical additives which help to provide an effective film layer for heavy-duty work.
The world of lubricants is constantly changing and new advances are made almost daily. The trend is towards lubricants that offer more than one feature - for example, a lubricant that offers protection against corrosion and can also be effective at higher temperatures.
he technology of lubrication has been used from the ancient times, from the pyramid building where massive rock slabs are moved, up to present modern times. In machineries, medical application, and leisure. Lubrication means to make something run smooth, make something Slippery, to reduce friction on moving parts. In Tribology, lubricant is consisting of either oil or grease. Most grease is from animal fats or vegetable lard.
Proper lubrication eliminates the friction that totally contributes to this failure phenomenon. The lubricant stays in between the sliding matter and serves like roller bearings. It continuously reduces the coefficient of friction, thereby reducing the force to move and heat that leads to seizure, bonding and fire. The general purpose of lubrication is to separate the two sliding bodies to reduce friction.
The main purpose of lubrication is to reduce friction and wear in bearings or sliding components to prevent premature failure. The effects of lubrication may be briefly explained as follows: Reduction of Friction and Wear. Direct metallic contact between the bearing rings, rolling elements and cage, which are the basic components of a beari ng, is prevented by an oil fi lm that reduces the friction and wear in the contact areas. It prevents inter metallic contacts between slides by allowing film of lubricants preventing friction. Extension of Fatigue Life. The sliding or rolling fatigue life of bearings depends greatly upon the viscosity and film thickness between the rolling contact surfaces. A heavy film thickness prolongs fatigue life, while insufficient film thickness shortens it. Dissipation of Frictional Heat and Cooling. Circulating lubrication may be used to carry away frictional heat or heat transferred from the outside to prevent the bearing from overheating and the oil from deteriorating. Others. Adequate lubrication also helps to prevent foreign material from entering the bearings and guards against corrosion and rusting. Satisfactory bearing performance can be achieved by adopting the lubricating method that is most suitable for the particular application and operating conditions. In general, oil offers superior lubrication; however, grease lubrication allows a simpler structure around the bearings.
Bearing
Lubricant The Importance of Lubrication Sel ection for Ball Bearings
When a bearing must perform under demanding conditions, the lubricant selection becomes critical. Lubrication will affect life, torque, speed, noise, grease migration out gassing, temperature and rust prevention of the bearing.
Ball Bearing
Lubricant Types
Two basic types of lubricants available are oil and grease.
Applications that require extremely low torque or narrow range of torque variation are suited to use oil as a lubricant. Depending on the application, it is possible that an oil lubricant may not meet a specific requirement. Grease is an oil to which a thickener has been added. Oil
Oil is the basic lubricant for ball bearings. Previously most lubricating oil was refined from petroleum. Today, however, synthetic oils such as diesters, silicone polymers, and fluorinated compounds have found acceptance because of improvements in properties.
Compared to petroleum base oils, diesters in general have better low temperature properties, lower volatility, and better temperature/viscosity characteristics. Silicones and fluorinated compounds possess even lower volatility and wider temperature/viscosity properties. Grease
Grease is an oil to which a thickener has been added to prevent oil migration from the lubrication site. It is used in situations where frequent replenishment of the lubricant is undesirable or impossible. All of the oil types mentioned here can be used as grease bases to which are added metallic soaps, synthetic fillers and thickeners.
The operative properties of grease depend almost wholly on the base oil. Other factors being equal, the use of grease rather than oil results in higher starting and running torque and can limit the bearing to lower speeds.
Grease additives include rust inhibitors, extreme pressure additives (EP), oxidation preventatives, etc. Because
of the wide variety and complexity of additives, the characteristics of similar g reases change
considerably from one manufacturer to another. Oils and Base Fluids Petroleum Mineral Lubricants
Petroleum lubricants have excellent load carrying abilities and are naturally good against corrosion, but are useable only at moderate temperature ranges (-25º to 250 ºF). Grease s of this type would be recommended for use at moderate temperatures, light to heavy loads and moderate to high speeds. Super-Refined Petroleum Lubricants
While these lubricants are usable at higher temperatures than petroleum oils (-65 º to 350 ºF), they still exhibit the same excellent load carrying capacity. This further refinement eliminates unwanted properties, leaving only the desired chemicals chains.
Additives are introduced to increase the oxidation resistance, etc. Synthetic Lubricants
The esters, diesters and poly-a-olefins are probably the most common synthetic lubricants. They do not have the film strength capacity of a petroleum product, but do have a wide temperature range (-65º to 350 ºF) and are oxidation resistant.
Synthetic hydrocarbons are finding a greater use in the miniature and instrument ball bearing industry because they have proved to be a superior general purpose lubricant for a variety of speeds, temperatures and environments. Silicone Lubricants
Silicone products are useful over a much wider temper ature range (-100 º to 400 ºF), but do not have the load carrying ability of the petroleum types and other synthetics. It has become customary in the instrument and miniature bearing industry, in recent years, to derate the dynamic load rating (Cr)of a bearing to 1/3 of the value if a silicone product is used. Perfluorinated Polyether (PFPE)
Oils and greases of this type have found wide use where stability at extremely high temperatures and/or chemical inertness is required. This specialty lubricant has excellent load carrying capabilities but its inertness makes it less compatible to additives, and less corrosion resistant. Lubrication Methods
Grease packing to approximately one quarter to one third of a ball bearing's free volume is one of the most common methods of lubrication. Volumes can be controlled to a fraction of a percent for precision applications by special lubricators. In some instances, customers have requested that bearings be lubricated 100% full of grease. Excessive grease, however, is as detrimental to a bearing as insufficient grease. It causes shearing,heat buildup, unnecessarily high torque, and deterioration through constant churning which can ultimately result in bearing failure. Centrifuging an oil lubricated bearing removes excess oil and leaves only a very thin film on all surfaces. This method is used on very low torque bearings and can be specified by the customer for critical applications.
There are many lubricants available for ball bearings. You will find a chart at in the next page that lists a variety of types, one of which should work well for most operating conditions. Table of Commonly Used Lubricants Code L01
Ester oil
-60º to +250º
LY48
Synthetic oil + clay thickener
Basic
Type Oil
*Operating Temp. ºF
Uses
Low speed instrument oil. Rust preventative. Low torque. -65º to +350º
Developed for aircraft bearings and
mechanisms. OK for low-speed oscillation. Low torque. Considered noisy in bearings. LY121 Ester oil + lithium soap thickener
-40º to +300º
Very quiet, widely used motor grease.
HDD spindle motor applications. OK for low speed oscillation. LY694 Synthetic hydrocarbon and refined mineral oil + diurea soap thickener Encoders, HDD actuators applications. OK for high speed oscillation.
-50º to +300º
LY532 Ester oil + urea soap thickener -40º to +350º
Suitable for automotive radiator cooling fan
applications and other high temperature motor bearings. LY551 Poly-alpha-olefin oil + urea soap thickener
-40º to +300º
Vacuum cleaner and power tool
applications. Low noise and high speed.
Table of Commonly Used Lubricants Code L01
Ester oil
-60º to +250º
LY48
Synthetic oil + clay thickener
Basic
Type Oil
*Operating Temp. ºF
Uses
Low speed instrument oil. Rust preventative. Low torque. -65º to +350º
Developed for aircraft bearings and
mechanisms. OK for low-speed oscillation. Low torque. Considered noisy in bearings. LY121 Ester oil + lithium soap thickener
-40º to +300º
Very quiet, widely used motor grease.
HDD spindle motor applications. OK for low speed oscillation. LY694 Synthetic hydrocarbon and refined mineral oil + diurea soap thickener
-50º to +300º
Encoders, HDD actuators applications. OK for high speed oscillation. LY532 Ester oil + urea soap thickener -40º to +350º
Suitable for automotive radiator cooling fan
applications and other high temperature motor bearings. LY551 Poly-alpha-olefin oil + urea soap thickener applications. Low noise and high speed.
Components: Oil Service Rating The oil service rating is a set of letters printed on the oil can to denote how well the oil will perform under operating conditions. The American Petroleum Institute (API) sets this performance standard. The API system for rating oil classifies oil according to its performance characteristics. The
-40º to +300º
Vacuum cleaner and power tool
higher rated oils contain additives that provide maximum protection against rust, wear, oil oxidation, and thickening at high temperatures. The oil service ratings are as follows: 1. SAadequate for utility engines subjected to light loads, moderate speeds, and clean conditions. Contains no additives. 2. SBadequate for automotive use under favorable conditions (light loads, low speeds, and moderate temperatures) with relatively short oil change intervals. Generally offers only minimal protection to the engine against bearing scuffing, corrosion, and oil oxidation. 3. SCmeets oil warranty requirements for 1964 through 1967 automotive gasoline engines. 4. SDmeets oil warranty requirements for 1968 through 1970 automotive gasoline engines. Offers additional protection over SC oils that are necessary with the introduction of emission controls. 5. SEmeets oil warranty requirements for 1972 through 1979 automotive gasoline engines. Stricter emission requirements created the
need for this detergent oil. 6. SFmeets oil warranty requirements for 1980 through 1988 automotive gasoline engines. The SF oil is designed to meet the demands of small, high-revving engines. A SF oil can be used in all automotive vehicles requiring detergent oil. 7. SGmeets oil warranty requirements for 1989 through present automotive gasoline engines. Contains more additives than SF oils. Can be used as CC or diesel type oils. It is a detergent oil. 8. CAmeets all requirements for naturally aspirated diesel engines operated on low sulfur fuel. 9. 10. 11. The CBmeets all requirements for naturally aspirated diesel engines operated on high sulfur fuel. CCmeets all requirements for lightly supercharged diesel engines. CDmeets all requirements for moderately
supercharged diesel engines. operator's manual provides the service rating recommended for a specific vehicle. You can use a better service rating than recommended, but NEVER a lower service rating. A high service rating (SG, for example) can withstand higher temperatures and loads while still maintaining a lubricating film. It will have more oil additives to prevent oil oxidation, engine deposits, breakdown, foaming, and other problems. LUBRICATING (OIL) SYSTEM COMPONENTS It must be remembered that the lubricating system is actually an integral part of the engine and the operation of one depends upon the operation of the other. Thus the lubricating system, in actual practice, cannot be considered as a separate and independent system; it is part of the engine. The lubricating system basically consists of the following: Oil Panreservoir or storage area for engine oil. Oil Level Gaugechecks the amount of oil in the oil pan. Oil Pumpforces oil throughout the system. Oil Pickup and Strainerscarries oil to the pump and removes large particles. Oil Filtersstrains out impurities in the oil.
Oil Galleriesoil passages through the engine. Oil Pressure Indicatorwarns the operator of low oil pressure. Oil Pressure Gaugeregisters actual oil pressure in the engine. Oil Temperature Regulatorcontrols engine oil temperature on diesel engines. Oil Pan The oil pan, normally made of thin sh
History and raw-materials:
Since the Roman era, many liquids, including water, have been used as lubricants to minimize the friction, heat, and wear between mechanical parts in contact with each other. Today, lubricating oil, or lube oil, is the most commonly used lubricant because of its wide range of possible applications. The two basic categories of lube oil are mineral and synthetic. Mineral oils are refined from naturally occurring petroleum, or crude oil. Synthetic oils are manufactured polyalphaolefins, which are hydrocarbon-based polyglycols or ester oils.
Although there are many types of lube oils to choose from, mineral oils are the most commonly used because the supply of crude oil has rendered them i nexpensive; moreover, a large body of data on their properties and use already exists. Another advantage of mineral-based lube oils is that they can be produced in a wide range of viscositiesviscosity refers to the substance's resistance to flowfor diverse applications. They range from low-viscosity oils, which consist of hydrogen-carbon chains with molecular weights of around 200 atomic mass units (amu), to highly viscous lubricants with molecular weights as high as 1000 amu. Mineral-based oils with different viscosities can even be blended together to improve their performance in a gi ven application. The common 1OW-30 motor oil, for example, is a blend of low viscous oil (for easy starting at low temperatures) and highly viscous oil (for better motor protection at normal running temperatures).
First used in the aerospace industry, synthetic lubricants are usually formulated for a specific application to which mineral oils are ill-suited. For example, synthetics are used where extremely high operating temperatures are encountered or where the lube oil must be fire resistant. This article w ill focus on mineral-based lube oil. Raw Materials
Lube oils are just one of many fractions, or components, that can be derived from raw petroleum, which emerges from an oil well as a yellow-to-black, flammable, liquid mixture of thousands of hydrocarbons (organic compounds containing only carbon and hydrogen atoms, these occur in all fossil fuels). Petroleum deposits were formed by the decomposition of tiny plants and animals that lived about 400 million years ago. Due to climatic and geogr aphical changes occurring at that time in the Earth's history, the breakdown of these organisms varied from reg ion to region.
Because
of the different rates at which organic material decomposed in various places, the nature and
percentage of the resulting hydrocarbons vary widely. Consequently, so do the physical and chemical characteristics of the crude oils extracted from different sites. For example, while California crude has a specific gravity of 0.92 grams/milliliter, the lighter Pennsylvania crude has a specific gravity of 0.81 grams/milliliter. (Specific gravity, which refers to the ratio of a substance's weight to that of an equal volume of water, is an important aspect of crude oil.) Overall, the specific gravity of crudes range s between 0.80 and 0.97 grams/milliliter.
Depending on the application, chemicals called additives may be mixe d with the
Lubricating oil is refined from crude oil. After undergoing a purifying process colled sedimentation, the crude oil is heated in huge fractionating towers. The various vaporswhich can be used to make fuel, waxes, or propane, among other substancesboil off and are collected at different points in the tower. The lube oil that is collected is filtered, and the n additives are mixed in. refined oil to give it desired physical properties. Common additives include metals such as lead or metal sulphide, which enhance lube oil's ability to prevent galling and scoring when metal surfaces come in contact under extremely high pressures. High-molecular weight polymerics are another common additive: they improve viscosity, counteracting the tendency of oils to thin at high tem peratures. Nitrosomines are employed as antioxidants and corrosion inhibitors because they neutralize acids and form protective films on metal surfaces.
The Manufacturing Process
Lube oil is extracted from crude oil, w hich undergoes a preliminary purification process (sedimentation) before it is pumped into fractionating towers. A typical high-efficiency fractionating tower, 25 to 35 feet (7.6 to 10.6 meters) in diameter and up to 400 feet (122 meters) tall, is constructed of high grade steels to resist the corrosive compounds present in crude oils; inside, it i s fitted with an ascending series of condensate collecting trays. Within a tower, the thousands of hydrocarbons in crude oil ar e separated from each other by a process called fractional distillation. As the vapors rise up through the tower, the various fractions cool, condense, and return to liquid form at differe nt rates determined by their respective boiling points (the lower the boiling point of the fraction, the higher it rises before condensing). Natural gas reaches its boiling point first, followed by gasoline, kerosene, fuel oil, lubricants, and tars. Sedimentation 1 The crude oil is transported from the oil well to the refinery by pipeline or tanker ship. At the refinery, the oil undergoes sedimentation to remove any water and solid contaminants, such as sand and rock, that maybe suspended in it. During this process, the cr ude is pumped into large holding tanks, where the water and oil are allowed to separate and the contaminants settle out of the oil. Fractionating 2 Next, the crude oil is heated to about 700 degrees Fahrenheit (371 degrees Celsius). At this temperature it breaks down into a mixture of hot vapor and liquid that is then pumped into the bottom of the first of two fractionating towers. He re, the hot hydrocarbon vapors float upward. As they cool, they condense and are collected in different trays installed at different levels in the tower. In this tower, normal atmospheric pressure is maintained continuously, and about 80 percent of the crude oil vaporizes. 3 The remaining 20 percent of t he oil is then reheated and pumped into a second tower, wherein vacuum pressure lowers the residual oil's boiling point so that it can be made to vaporize at a lower temperature. The heavier compounds with higher boiling points, such as tar and the inorganic compounds, remain behind for further processing. Filtering and solvent extraction 4 After further processing to remove unwanted compounds, the lube oil that has been collected in the two fractionating towers is passed through several ultrafine filters, which remove remaining impurities. Aromatics, one such contaminant, contain six-carbon rings that would affect the lube oil's v iscosity if they weren't removed in a process called solvent extraction. Solvent extraction is possible because aromatics are more soluble in the solvent than the lube oil fraction is. When the lube oil is treated with
the solvent, the aromatics dissolve; later, after the solv ent has been removed, the aromatics can be recovered from it. Additives, inspection, and packaging 5 Finally, the oil is mixed with additives to give it the desired physical properties (such as the ability to withstand low temperatures). At this point, the lube oil is subjected to a variety of quality control tests that assess its viscosity, specific gravity, color, flash, and fire points. Oil that meets quality standards is then packaged for sale and distribution. Quality Control
Most applications of lube oils require that they be nonresinous, pale-colored, odorless, and oxidationresistant. Over a dozen physical and chemical tests are used to classify and determine the grade of lubricating oils. Common physical tests include measurements for viscosity, specific gravity, and color, while typical chemical tests include those for flash and fire points.
Of all the properties, viscosity, a lube oil's resi stance to flow at specific temperatures and pressure s, is probably the single most important one. The application and operating temperature range are key factors in determining the proper viscosity for an oil. For e xample, if the oil is too viscous, it offers too much resistance to the metal parts moving ag ainst each other. On the other hand, if it not viscous enough, it will be squeezed out from between the mating surfaces and will not be able to lubricate them sufficiently. The Saybolt Standard Universal Viscometer is the standard instrument for determining viscosity of petroleum lubricants between 70 and 210 deg rees Fahrenheit (21 and 99 degrees C elsius). Viscosity is measured in the Say bolt Universal second, which is the time in seconds required for 50 milliliters of oil to empty out of a Saybolt viscometer c up through a calibrated tube orifice at a g iven temperature.
The specific gravity of an oil depends on the refi ning method and the types of additives present, such as lead, which gives the lube oil the ability to resist extreme mating surface pressure and cold temperatures. The lube oil's color indicates the uniformity of a particular g rade or brand. The oil's flash and fire points vary with the crude oil's origin. The flash point is the temperature to which an oil has to be heated until sufficient flammable vapor is driven off so that it will flash when brought into contact with a flame. The fire point is the higher temperature at which the oil vapor will continue to burn when ignited.
Common engine oils are classified by viscosity and performance according to specifications established by the Society of Automotive Engineers (SAE). Performance factors include wear prevention, oil sludge deposit formation, and oil thickening. The Future
The future of mineral-based lubricating oil is limited, because the natural supplies of petroleum are both finite and non-renewable. Experts estimate the total recoverable light to medium petroleum reserves at 1.6 trillion barrels, of which a third has been used. Thus, synthetic-based oils will probably be increasingly important as natural reserves dwindle. This is true not only for lubricating oil but also for the other products that result from petroleum refining.
Abstract
Lubricants based on renewable raw materials and their derivatives are drawing increased attraction in various applications. Here, the environmental awareness is the key factor of succe ss. The use of such rapidly biodegradable materials is especially favourable in loss-lubrication and hydraulic systems with increased risk of damage. Environmentally friendly, biodegradable alternatives are available for a large variety of mineral oil based lubricants. The substitution of mineral oil with biodegradable base oils is a primary objective. Vegetable oils are the m ajor source of these base fluids. Compared to conventional mineral oil based fluids most of such substances exhibit lower thermal and oxidation stability and even worse low-temperature behaviour. These physical and chemical properties can be improved by chemical modification. This review covers chemical reactions performed on fatty compounds on both laboratory and industrial scale. Economic processes are presented as well as new reactions with potential market value. Alternative routes to improved rapidly biodegradable base fluids are mentioned too, e.g. breeding successes with high oleic sunflower oil.
